Key result
Familial DCM phospholamban mutations reduce phosphorylation by altering conformation and weakening PKA interactions.
Why the study?
Mutations in phospholamban (PLN) are linked to familial dilated cardiomyopathy and heart failure, but the underlying molecular mechanism remains controversial.
Do DCM-associated mutations in phospholamban alter its conformation and interaction with protein kinase A, thereby reducing phosphorylation levels?
Do DCM-associated mutations in phospholamban alter its conformation and interaction with protein kinase A, thereby reducing phosphorylation levels?
Structural and biochemical analyses reveal that familial DCM mutations in phospholamban reduce its phosphorylation by weakening its interaction with PKA, elucidating a key pathological mechanism.
Preclinical only; leaves open whether restoring phospholamban-PKA interaction alters progression in human familial DCM.
Several mutations identified in phospholamban (PLN) have been linked to familial dilated cardiomyopathy (DCM) and heart failure, yet the underlying molecular mechanism remains controversial. PLN interacts with sarco/endoplasmic reticulum Ca 2+ -ATPase (SERCA) and regulates calcium uptake, which is modulated by the protein kinase A (PKA)-dependent phosphorylation of PLN during the fight-or-flight response. Here, we present the crystal structures of the catalytic domain of PKA in complex with wild-type and DCM-mutant PLNs. Our structures, combined with the results from other biophysical and biochemical assays, reveal a common disease mechanism: the mutations in PLN reduce its phosphorylation level by changing its conformation and weakening its interactions with PKA. In addition, we demonstrate that another more ubiquitous SERCA-regulatory peptide, called another-regulin (ALN), shares a similar mechanism mediated by PKA in regulating SERCA activity. Significance Dilated cardiomyopathy (DCM) is a common type of heart disease. Familial DCM is associated with mutations on phospholamban (PLN), but the mechanism remains elusive. Phosphorylation of PLN is known to influence its physiological function. We hypothesize that the connection between such mutations and DCM may involve decreased PLN phosphorylation levels due to less efficient binding to protein kinase A. We utilize x-ray crystallography, SPR, enzyme kinetic assays, thermal melt assays, and NMR to examine the structural and energetic consequences for PKA-catalyzed phosphorylation of PLN variants containing DCM-associated mutations. Our results provide a foundation to understand the general working mechanism of PKA and the physiological regulation of PLN by PKA, and also provide important insight into the pathological mechanism of DCM.
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Qin et al. (2021) studied Familial dilated cardiomyopathy. PKA-catalyzed phosphorylation of PLN variants vs. Wild-type PLN was evaluated on Structural and energetic consequences for PKA-catalyzed phosphorylation. Mutations in phospholamban associated with familial dilated cardiomyopathy reduce its phosphorylation level by changing its conformation and weakening its interactions with protein kinase A.
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